A performance of an information processing system depends upon the speed of an arithmetic operation apparatus and a mutual coupling medium, and the speed of the arithmetic operation apparatus continuously implements rapid improvement by scaling by fine processing of integration circuits (for example, silicon integration circuits).
According to the rapid improvement of the speed of the arithmetic operation apparatus, also increase of the speed of the mutual coupling medium is required, and significant downsizing and increase in speed are demanded.
What is drawing attention as means for this is mutual coupling by optical communication in which an optical integration circuit (for example, a silicon integration circuit) and an optical fiber are used.
One of technologies for improving the speed per one optical fiber is wavelength division multiplexing (WDM).
Where this WDM is used, a technology for demultiplexing a WDM signal into a plurality of optical signals having wavelengths different from each other (Demultiplex: Dmx) is demanded.